The invention applies to the manufacture of flat tension mask color cathode ray tubes. More specifically, the invention provides means for achieving registration of the aperture patterns of flat tension shadow masks and related cathodoluminescent screens.
In particular, the invention relates to a portion of the process steps employed in the manufacture of the front glass panel assembly of a flat tension mask color cathode ray tube. The front glass panel assembly includes a glass front panel, a support structure on the inner surface of the front glass panel and a tensed foil shadow mask affixed to the support structure.
In this specification, the terms "grille" and "screen" are used, and apply generally to the pattern on the inner surface of the front panel. The grille, also known as the black surround, or black matrix, is widely used to enhance contrast. It is applied to the panel first. It comprises a dark coating on the panel in which holes are formed to permit passage of light, and over which the respective colored-light-emitting phosphors are deposited to form the screen.
The holes in the grille must register with the columns of electrons passed by the holes or slots in the shadow mask. This is the primary registration requirement in a grille-equipped tube; the phosphor deposits may overlap the grille holes, hence their registration requirements are less precise.
In tubes without a grille, on the other hand, it is the phosphor deposits which must register with the columns of electrons. The word "screen", when used in the context of registration, therefor includes the grille where a grille is employed, as well as the phosphor deposits when there is no grille.
Historically, color cathode ray tubes have been manufactured by requiring that a shadow mask dedicated to a particular panel follow the panel through various states of the manufacturing process. Such a procedure is more complex than might be obvious; a complex conveyor system is needed to maintain the marriage of each mask assembly to its associated panel throughout the manufacturing process. In several stages of the process the panel must be separated from the mask, and the mating shadow mask cataloged for later reunion with its panel mate.
With the recent commercial introduction of the flat tension mask cathode ray tube, many process problems related to the curvature of the mask and panel have been alleviated or reduced. Necessarily, however, initial production of flat tension mask tubes has been based on continued use of the proven technology of mating a dedicated mask to a specific front glass panel throughout the manufacturing process. However, because the flat tension mask requires tension forces during the manufacturing process as well as after installation in a tube, somewhat cumbersome in-process support frames become necessary. These introduce complexity and expense in the manufacture of color cathode ray tubes of the tension mask type.
Thus the desirability of simplifying the conventional production process remains as great as ever in the manufacture of cathode ray tubes of the flat tension mask type.
It has been recognized that color tube manufacture would be simplified if any mask could be registered with any screen (commonly termed an "interchangeable" mask), so that masks and screens would no longer have to be individually mated. Yet to this day, no commercially viable approach suitable for achieving such component interchangeability has been implemented or disclosed.
______________________________________ Known Prior Art ______________________________________ 2,625,734 Law 2,733,366 Grimm 3,437,482 Yamada, et al. 3,451,812 Tamura 3,494,267 Schwartz 3,563,737 Jonkers 3,638,063 Tachikawa 3,676,914 Fiore 3,768,385 Noquchi 3,889,329 Fazlin 3,894,321 Moore 3,983,613 Palac 3,989,524 Palac 4,593,224 Palac 4,692,660 Adler 4,695,761 Fendley FR1,477,706 Gobain GB2,052,148 Sony 20853/65 Japanese ______________________________________ Article "Improvements in the RCA Three Beam ShadowMask Color Kinescope", Grimes, 1954, Proceedings of the IRE, January, 1954, pgs. 315-326.
According to the parent applications, a manufacturing apparatus and process for color cathode ray tubes of the flat tension mask type is described wherein shadow masks and front panels are respectively interchangeable during front panel assembly.
This method achieves practical interchangeability of shadow masks in the manufacture of flat tension mask color cathode ray tubes by providing automatic means for adjusting the postion size and/or shape of a mask such that its aperture pattern is brought into registration with a standard pattern.
More specifically, a method and associated apparatus is shown for changing a geometrical parameter of the mask pattern to achieve coincidence with a standard pattern which bears a fixed geometrical relationship to a predetermined screen pattern.
A position sensing means and a feedback control system is also shown and described in the parent application for applying controlled forces at a plurality of locations about the periphery of the mask for the purpose of moving the mask to a desired position and stretching it to a desired size and shape.
In both the parent applications an apparatus is schematically disclosed for changing the geometric configuration of the mask to achieve coincidence with a standard pattern that includes a stretching device consisting of clamps and links that applies a distribution of forces according to predetermined ratios around the periphery of the mask. It has been found that reduction rolling of the metal coils from which the masks are made, and particularly the rolling direction, appears to cause horizontal skewing during the initial stretching manipulation. The mask blank strain relieving process also appears to vary the position of the reference apertures in the mask from one mask to another.
It is an object of this invention to provide manufacturing apparatus for color cathode ray tubes of the flat tension mask type wherein shadow masks and front panels are respectively interchangeable during front panel assembly.
It is also an object of the invention to provide a system for achieving practical interchangeability of shadow masks in the manufacture of flat tension mask color cathode ray tubes by providing automatic means for adjusting the position size and/or shape of a mask such that its aperture pattern is brought into registration with a screen pattern.
It is a further object to provide such a system which compensates for screen position and geometry errors.
It is an object of this invention to provide, in a manufacturing process for color cathode ray tubes of the flat tension mask type wherein shadow masks and front panels are respectively interchangeable during front panel assembly, an apparatus for changing a geometrical parameter of the mask pattern to achieve coincidence with a screen pattern.
It is a principal object of the present invention to provide a completely automated system that includes an assembly system for flat tension masks and faceplates including a transport shuttle for conveying a face panel module and a mask module altenately to an assembly station where the mask and panel are registered to one another and joined, with a minimum of part movement.
It is also an object of the present invention to provide a complete assembly system for flat tension masks and panels with a transporting system that includes identical faceplate and mask modules that convey the masks and faceplates to an assembly station, where the modules are designed to facilitate registration at the assembly station.
It is a still further object of the present invention to provide a complete assembly system for flat tension masks and faceplates where the faceplate is interrogated at a faceplate loading station to determine the position of the faceplate bearing screen with respect to the faceplate module to eliminate the need to accomplish this task at the assembly station.
It is another object of the present invention to provide a complete assembly system for flat tension masks and faceplates where all of the optical interrogating devices are carried on mask and panel modules to eliminate swing frames for these optical devices at the assembly station.
It is still another objection of the present invention to provide a complete assembly system for flat tension masks and faceplates where fiducial marks are provided on the viewer side or the opposite side of the faceplate outside the perimeter of the faceplate screen to identify the location of the screen on the faceplate, and an optical system for sensing these fiducial marks.